Butterfly Basics, Part 1

Butterflies, one of my favorite groups of organisms to work with, are equally as complex and interesting as they are beautiful. Here are a few answers to common questions I get about them as I walk around the lodges with a jar full of stinky rotten banana butterfly bait:

Hey Phil, what are you doing with that jar full of stinky rotten bananas?

Rotten fruit is a staple food source for a lot of butterflies (more info below),

Cithaerias pireta, often seen along trails in the Amazon.

Image by Phil Torres

and making a rotten fruit bait to place in a trap is a great way to sample butterflies without harming them.

My recipe: 6 mashed, rotten bananas (3 with peel, 3 without), 1/4 cup of sugar, half cup of beer, and half cup of water. Put in a jar in the sun for 3-5 days, shake and release the gas build up every morning and night. It doesn’t smell great, but butterflies love it. And it smells much better than my rotten fish bait I use as well.What do butterflies eat?

Just like in the rest of the world, many butterflies in the tropics feed on nectar. Nectar provides a great source of energy essential for active flying and reproduction. However, butterflies here also feed on a variety of other sources, for a variety of reasons, including: mud, wet stones, feces, tree sap, rotten fallen fruit, urine, carrion, bird droppings, fungi, animal secretions, and pollen. Many of those food items provide male butterflies with the minerals and organic compounds necessary to create a pheromone, or chemical scent, to attract a female.

The white hairs visible here smell great. These are the pheromone-emitting androconial hairs, which in this case smell like fruit loops. Image by Phil Torres

Additionally, the neotropics (New World tropics like Peru) are home to the only group of butterflies that have adapted the feed on protein-rich pollen, the Heliconius butterflies, giving them an advantage over many butterflies in being able to live for 2-3 months, rather than 2-3 weeks like most butterflies. Butterfly feeding is one of the many areas of their biology that hasn’t been studied thoroughly. Scientists don’t know, for example, why some butterflies prefer to feed on rotten fruit over nectar when they have similar sugar compounds.

Why do butterflies have bright colors?

The colorful Morpho menelaus makes me happy.

In general, the bright colors are used to deliver a message. That message may be for a conspecific (butterfly of the same species), showing that they are either suitable/nonsuitable to mate or to let a male know they are in another male’s territory (you can wave a blue handkerchief at a male blue morpho and get a quick aggressive response).

The colors are also used as a message to predators like birds or monkeys, stating clearly: don’t eat me, I’m poisonous.

Many butterflies have evolved to tolerate poisonous plants as a caterpillar and use those toxins against predators. Birds tend to learn pretty quickly, and if a bright orange and black butterfly causes it to get sick once, it likely won’t try to eat one again. This does get complicated when butterflies that taste delicious to birds mimic the poisonous butterflies, only pretending to be toxic (called Batesian mimicry), but we’ll save that discussion for another time.

Many butterflies gather on the muddy river shore to feed on minerals in the sand.Image by Phil Torres